1. Field of the Invention
The present invention relates to a technique for grounding a flexible circuit board that can be assembled into a head gimbal assembly of a hard disk drive.
2. Background Information
Hard disk drives typically contain a plurality of heads that are magnetically coupled to a number of rotating disks. The heads can both magnetize and sense the magnetic fields of the disks, to store and retrieve data as is known in the art.
Each head is typically gimbal mounted to the end of a corresponding suspension arm. The suspension arms are attached to an actuator arm assembly. The actuator arm assembly includes a voice coil motor that can swing the arm and move the heads across the surfaces of the disks. The data is typically stored within annular tracks that extend radially across the surfaces of the disks. The voice coil motor moves the actuator and suspension arms so that the heads can access the different tracks.
There are various types of magnetic recording heads including magneto-resistive ("MR") and giant magneto-resistive ("GMR") heads. MR and GMR heads contain a write element for magnetizing a corresponding disk surface and a separate read element for sensing the magnetic fields of the disks. The heads are connected to electrical circuits that excite the write elements and sense a voltage across the read elements.
The heads may be connected to the electrical circuits by a flexible circuit board that is attached to the suspension arm. The flexible circuit board typically has a plurality of conductive pre-amp pads that are connected to a pre-amplifier and a number of conductive head pads that are connected to a head. The pre-amp pads are coupled to the head pads by a plurality of conductive traces that extend along a dielectric substrate of the flexible circuit board. The dielectric substrate is typically constructed from a flexible material such as a polyimide.
It is desirable to test the heads before installation into the disk drive assembly. The heads are typically assembled to the flexible circuit board and then manually loaded into a dynamic head tester. It has been found that manually loading the heads may result in an electrostatic discharge ("ESD") that may damage the read and write elements. MR and GMR are heads are particularly sensitive to ESD events. It would be desirable to provide a flexible circuit board and assembly process which reduces the likelihood of head damage from an electrostatic discharge.